People can buy Pixels with GrapheneOS preinstalled from a bunch of companies despite it not being shipped that way from the factory.

Pixels are currently the only devices providing the required updates and hardware security features. There will be at least one Motorola flagship with GrapheneOS support in 2027 meeting the same requirements. It will expand to more Motorola devices from there. iOS only runs on iPhones but that's hardly a barrier to adoption for it. Pixels aren't quite broadly available enough and it will take time before we can support lower end Motorola devices in the same price range as an 'a' series Pixel.

The vast majority of Android apps do work. Banking apps are a special case where around 10% don't work due to banning using a non-Google-certified OS. Most banking apps definitely work on GrapheneOS.